Preheat oven to 350 degrees F. Bring large pot of water to boil. Peel, wash, and quarter potatoes. Put potatoes in boiling water and cook until very tender.
Drain and put potatoes in large bowl or food processor. Mash potatoes with soymilk and margarine--use more or less to achieve desired consistency. Add salt and pepper to taste.
Arrange hot dog buns open-faced on an ungreased cookie sheet. Thaw soy dogs if frozen, and slice each soy dog in half long-ways. Place 1/2 soy dog on each side of a bun. Spread mashed potatoes on top of soydogs. Sprinkle with soy cheddar. Bake for 10 minutes or until soy cheddar is melted and buns are slightly toasted.
I serve this with steamed vegetables, and fresh fruit. It is a carbtastic meal, and my family loves it!